When it comes to fodder beet yield, it is easy to focus on what happens at the end of the season. But a large part of the crop’s yield potential is being determined much earlier.
The reason comes back to one of the fundamentals of fodder beet physiology: growth is driven by thermal time, not simply days on the calendar. And when the crop accumulates that thermal time can be just as important as how much it receives across the entire season.
A season that looked better on paper than it did in the paddock
Last season was a good example. Across the season from October through to March, growing degree days were actually around 4% above the long-term average. On paper, that does not sound like a season that should have struggled for growth.
The problem was the distribution. January and February are a critical period for fodder beet bulb development, when an established crop has the potential to be growing at around 300kg DM/ha/day. Last season, those months did not deliver.
January recorded around 83 fewer sunshine hours than the long-term average, followed by approximately 30 fewer hours in February. So while the season's total thermal time looked relatively good, the crop did not necessarily receive the heat and radiation when it could make the greatest use of it.
That is an important distinction. It is not just how much growing opportunity a crop gets. It is whether the crop is ready to capture it when it arrives.
Think of the canopy as a solar panel
One of the simplest ways to think about fodder beet is that we're trying to grow a solar panel. The canopy captures sunlight and the plant converts that energy into growth and, ultimately, bulb yield.
As the crop moves through canopy establishment and its vegetative stages, it accumulates thermal time. At approximately the 25-leaf stage it moves into its peak bulb-filling period. That peak growth window occurs at roughly 1,244 to 1,673 accumulated growing degree days.
The opportunity is significant. At its physiological peak, fodder beet can be adding around 300kg DM/ha/day. But that window doesn't stay open forever.
If the crop reaches peak canopy and bulb development after maximum summer radiation has already passed, it has missed part of its opportunity. March can't necessarily make up for what was lost in January or February. That's why establishment timing matters.
What difference can three weeks make?
Last season provided a useful real-world comparison. Two adjacent blocks were planted using the same cultivar, same preparation, same sowing rate and same herbicide programme.
The first 60ha block was planted on 23 September. A second 40ha block was planted 21 days later, on 14 October.
The difference? The earlier crop accumulated an additional 235 growing degree days before entering the poorer summer growth period and ultimately yielded 1.5t DM/ha more.
That doesn't mean every crop should automatically be planted three weeks earlier. But it does demonstrate what additional time can give the crop when the conditions are right.
The earlier crop entered summer with more thermal time already banked. When January and February delivered less than expected, it had more margin. The later crop had less.
Canopy closure by Christmas
For crops targeting high yields, one of the objectives should be to have a strong, functioning canopy in place to intercept as much peak summer radiation as possible.
Lincoln University sowing-date data discussed during our recent Catalyst technical training helps demonstrate why. A mid-September-sown crop missed around 6.4% of the available peak radiation, while at the other extreme, a December-sown crop could miss up to 40%.
Earlier-sown crops were able to achieve a much closer match between peak canopy development and peak incoming radiation. That's where the yield opportunity sits.
In practical terms, canopy cover and closure by Christmas can put the crop in a much stronger position to capitalise on January and February growth.
But earlier isn't automatically better
There is an important caveat. This isn't about chasing a date on the calendar at the expense of everything else.
An early crop planted into poor conditions with a compromised seedbed or uneven establishment isn't suddenly a high-yielding crop simply because it went into the ground in September. Seedbed quality, plant population and establishment still come first.
Soil conditions need to be suitable. The paddock needs to be the right candidate. And the management programme needs to match the decision to plant earlier.
Early-sown fodder beet can also establish more slowly in cooler conditions. The crop may be accumulating thermal time more slowly, but the weeds aren't necessarily going to wait for it. That makes the pre-emergence programme and early weed control particularly important.
Going earlier is not just a planting-date decision. It is a management system.
It is about giving the crop a chance
No two seasons are the same, and planting earlier can not guarantee what January or February will deliver. What it can do, where soil and paddock conditions allow, is give the crop more opportunity to establish its canopy and accumulate thermal time before that critical summer growth period.
Last season demonstrated why that margin can matter. When the weather turned against crop growth during January and February, the crops that arrived at that period further developed were in a better position to keep moving.
As planting approaches this spring, the question isn't simply: “What date do we normally plant fodder beet?”
A better question is: “How do we have this crop in the best possible position to capture the growing opportunity when it arrives?”
That conversation starts with paddock selection, soil and seedbed conditions, planting timing, population and a weed-control programme capable of supporting the crop through establishment.
Talk to your local Catalyst agronomist about your fodder beet plan this spring and where there may be an opportunity to give your crop more time to perform.